Legal Advice (Hong Kong)

The company is refusing to give me my last paycheck because I didn't give a month's notice. However, my contract didn't specify that was necessary. The company is also asking for my help in the transition, but I don't want to if they continue to refuse to pay me.

I'm concerned they may try to sue me. Will they be able to if they never even finalized my work visa and paid me in cash? (I worked at the company for over 4 months, and the visa is still in process.)